Prepare the filling by blending cream cheese, powdered sugar, milk, and a splash of vanilla extract together until smooth and creamy—no streaks of sugar or lumps of cream cheese should remain at this stage.

In a separate bowl, whisk together the milk, eggs, half of the vanilla extract, cinnamon powder, and ground nutmeg until completely blended and the spices are evenly distributed.

Grease a large casserole dish. Layer half of the cubed French bread in the bottom, making sure the pan is covered with a thick, even layer.

Spoon or dollop the cream cheese mixture across the bread layer, letting some sink in and some remain visible for those pretty swirls. Scatter half the blueberries over this layer.

Top with the remaining bread cubes for the final bread layer. Sprinkle the rest of the blueberries over the top for bright color and bold bursts of flavor.

Slowly pour the custard mixture evenly over the entire casserole, ensuring every corner is soaked. Press down gently with a spatula to help the bread absorb the liquid if needed.

Cover the casserole and refrigerate overnight (or at least several hours) so the bread soaks all that custard—this is where the magic really happens.

Bake uncovered in a preheated oven until the edges turn beautifully golden brown and the center is puffed and slightly firm—the top should look toasted but not dry.

Let your casserole rest for a few minutes before slicing. This helps the structure set up for neat squares and gooey, creamy centers with every piece.